Control circuit



y 1952 B. RUDOLPH 2,604,612

CONTROL CIRCUIT Filed Dec. 13, 1946 ,FIE.1.

Line Vo/zage IN VEN TOR. Onie d Puoboh BY Patented July 22, 1952 CONTROL CIRCUIT QnioBI fludolph flakltidge, Tenn, assignor, by mesne. assignments, to the, UnitediStates. .ofi America; 1 as represented by the 1 United; States -AtomicrEnergyCommission Application Decemben13, 1946-, Serial No.1 71.6;926; I

My; invention: relates! to, alternating; current; control 1 circuits and more, particularly, to full.

w.aaieailternating currentcontrol circuitstfor. con:

trollingtheopcwer supplied {to aloadahd. is espe:

ciallyapplicablecfor.controlling thespeediof .A.,..C. motors;

Thyratronfandsotherlelectricniischarge,deyices;

haying the characteristiccthatacertain potential upon the .gridmill oausethem .to become :oonducting and. thereaitenjoonduct until the; anode...

potentia1...ialls below. a: predetermined minimum. havea'been used forthe control "of current from an alternating, current powersourceto aloacl.v By

controlling; the. timeeinthe cycle, at l which. the potentials upon, the. grids .of the tubes become.

sufiicient-tolendenthem conducting, the portions oijithercycle inwhioh ,thetub'es. will deliver cur:

rent .to .adoadjs,conttolledQand; thusthe average value of the .currentLdcHvered to theloadis rogue lated.;.

In order to'take eredby both lhalves of .the. .cycle,-. it has been the practice to. connect; as-filled" tubessuch as thyratrons, in. back .t'(U?}m1 relation. However, it 1's..customar.y, ;to individually; control the thyra? tronsrthrouehuse'of'gauxillary tubes which .must in,,.turn be controlled"byptherfmeans Apnl cantiwith. arkriowledge of 'fthese. problems in the prior; art has i forfan object: of his invention the provision of anelectronicgcontrol circuit whichcpermits 11111 f, wave control. and which re-' sponds ,to; thev controlfof. only; one of lth e tubes .of theicontrolcircuiti. p

Applicant hasas'another object of'ihis invention: the. provision 101 arthyratron control circuit providingr iull ware control of an: alternating current 'line; p

Applicant hasas another objectof hisinvention the provision pita" full wave control circuit wherein the control'tubes 'are connected in. back tobiac .rclation. andfrespondytothej application o1 w.ascontrol"signal," I

Applicant: has ',as-another.:obj ect of his invention the. provision. oftanalternatinacurrent volt: age -,.controlledcircint whereinas. tubes .con-. nected in;. flc'1,': ic1 .-to.backfi-lrelationarecontrolledv by; the.-'..applicationi,oI a" control lsi nal Lto one .of thetflbes...

Applicanthas. as ;.,another;obj actor-(his; inven: tlonthe.@myisiomotfa;joontrolijelement.011.one of. .a;pair of tubes.employed.tocontrolalternating current ,volta'ge; in order; to. synchronize it ,with the other tube. 7

Appl cant hasias,a-fiurthertobjectoi his inventiornthe:provisionof.analtematin rrent.volt:

advantageioijthe powerideliy- 4;0laims.; (Cl. 3155 -1977 )1 age control.,circuitwherein .out. of phase .voltag es. operate in. conjunction. .with. a .controlledj signal.

to; control :the .power fed. tonaload.

Other .obj ects. .and.advantagesof my invention will appear. from \the following.- specification and.

accompanying drawings, andthehoveljeatures thereof will be=particmarly,.p0inted outinhtlie.

annexed claims.

In .the..drawings,. Fig, 1. is a. schematicoof. my improved .full wave alternating cnrrentlrlegulat ing circuitv employing back. to. back connected 2.. is: a; schematic. of

thyratron gas tubes line and. control .voltagesvshown in graphical fornL.

Referring. to the designate. a pairiof-gas=filledItubessuchas thyratrons or the. like-.connectediin.back. to back relation, that is,.,the.jcathode .cr." tube. I is connected to the. .anodeof. tube. 2.; and the. anode of tube I: is-connected. to. the cathode ofjtuber 2;. Thistube .combinationislconnected inseriswith. one. side of .Lthe .power -line..3 :so ,that'the. power is. fedifrom .the alternating vcurrent power source A through the line 3, and tubes .l1and.2..to.the.1oad..5.l

Bridged across the. line in;para11el.- is :a resist.- ance combination. a'ndla resistanceccapacitance. combination. The: resistance" combination in! cludes, aIpair. otiresistances, 6,}1 connected; .in series,- while the. resistance capacitance combine) tion includes a condenserB and zresis'tance .9connected in -series., Bridged ,acrossthe-junctures ofthe. elements of the. resistance ecombination t'; I;

and the resistance. -.capacitance. combination $3, 9' is. the. primary winding, .1 0 oi-a transformer whose secondariesfll and ll-formparts of the griel cir-r cuitsrof tubes I 2.as described more -inedetail hereinafteiz. The :foregoing-;.constitutes a. phase. shifting network \for providing. the transformer Witha leading current and .-a-lagging.;-voltage.-.-.

The. grid circuit of tubecl includes. a resistance I 3 connectedrin series, with transformer: secondary, I Land- ;a source. of,.;g rid bias. [-41- This gridbiassourcel dkmay befa .battery,or-rectifienorrany other. suitablersource; of. D. C..voltage.:. These elements make up .,the: grid to; cathode circuitof tube L. Bridged-,;.across.rtheeresistanoe .13.- isva signal. or controls'ourca, ltamay take; any lsuitable form such; as a battery, I 5-;- and variable resistor I6... However, the. signalisourcetmaytake any; other, appropriate-forms,and,.is. not .tolhbe considered. as. restrictecL to. thee. embodiment shownfinthe. drawings... I J I 1 Connected across the plate to cathode ofitube 2 is arectifierll'l preterablyof theohardtube type, n .series @witlimal resistance; l S andaeYparaHeL-Lre 7 drawings.inwdetaili. I. and. 2

In its operation, the application of power to line 3 from source 4 impresses a voltage across tubes I and 2. When no signal is impressed across the resistance I3, the tube is biased to cut off by source I4, and the tube I does not fire. This places the entire line voltage across tube 2 since the two tubes are connected in "back to across rectifier I'I causing it to break down and current to flow through the circuit including resistances I8 and I9 during alternate half cycles. This creates a voltage drop across resistance I9 and stores up electrical energy in condenser 21!.

During the other half cycle when tube II is not operating, condenser 20 discharges through resistance I9, continuing the negative bias placed upon the grid of tube 2 by the flow of current through rectifier I'I duringthe other half cycle. The constants of the circuit may be made such that tube 2 will be biased to cut off during the whole of the half cycle'when tube I1 is not in operation. In other words, the size of resistance I9 and the capacity of condenser 20 may be such that flow through resistance I9 from condenser 20 will continue during the half cycle while tube I1 is not in operation. In this way both tubes I and 2 may be rendered inoperative during both halves of the cycle by the application of grid bias to the grid of tube I from the source I4. This is.

accomplished by adjusting the moving contact of resistance I6 to increase. or decrease the voltage drop across resistance I3. However, when a signal or positive potential is applied to the grid of tube I through the control circuit I5, I 6 to overcome the negative bias of element I4, the tube I .is caused to fire over allor a portion of the half cycle of alternating current fed to the load, depending upon the voltage lag insecondary winding which is generally fixed at about 7 0 lag. Over this same half cycle the voltage impressedacrosshigh vacuum or gas rectifier tube II causes it to fire since the anodes and cathodes .plates of the condenser 20 and at thesame timeplaces a bias on the grid of tube 2. Since tube I' is firing during the half cycle, the voltage across tube I1 and the network I8, I9 and 20 is proportionately lower as the voltage "across tube I, during the period of firing, is reduced. Under these conditions the charge built up on condenser 20 is not nearly as great as that built up on the condenser when tube I is not firing. Thus, it is seen that the charge built up on condenser 20 is proportional to the voltage across tube I. Accordingly, during the times when tube I is firing, the charge built up on condenser 20 will not be sufficient to prevent tube 2 from firing in the other half cycle. However, this may be adjusted somewhat by regulating the position of movable con-' tact 2 I bac relation. Line voltage is also impressed On the next half cycle neither tube I nor diode rectifier I'I fire, and, if the constants of the cir'- cuit are so chosen, the flow of current from condenser 20 through resistance I 9, during this time, will not be suificient to prevent operation of tube 2. This tube will then fire over as much of the half cycle as is permitted by the lagging voltage provided by the secondary, of. the transformer, and the bias provided by the condenser'20 and resistance I9.

I From the foregoing it will be seen that the period of operation over any half cycle of tubes I and 2 is determined bythe lag of the voltage in the secondary windings II and I2 of the transformer and'the grid bias provided by the source I 4 as afiectedby, the positive signal and the drop acrossresistance I3. The greater the lag of the voltage in secondary windings II and I2, the shorter the period of fire during any half cycle. It will thus be seen from the graph of Fig. 2 that where a line extending perpendicular from the base line at thepoint of intersection therewith of the lagging secondary voltage curve, intersects the linevoltage' curve, as at a and b, the respective tubes commence to fire and continue to fire until the line voltage curve crosses the base line,'as at c, d. By changing the lag in voltage," it is seen that the tubes I, 2 may be made to "conduct over a greater or lesser portion of the cycle The positive signal appliedtoitube I controls its operation, and this in turn controls the operation of. tube 2 since the voltage drop across'tube I determines the charge built up on condenser 20,.

and this in turn, determines the length of time during each half cyclewhen the tube 2is permitted to operate. When the circuit is properly adjusted, the second thyratron tube 2 williollow the first thyratron tube I providing identical cutofi points, except for polarity, for both halves of a cycle. This in turnwill determine and control the power fed to the load 5 so that accurate voltage control and regulation may be secured with a simple adjustment.

Having thusdescribed myinvention, I cam-1 '1. A full waveelectrical control circuit of the character described'comprising anelectrical dis-i charge device, a second electric. discharge device coupled to said first.electricdischarge deviceso that said discharge devices operate only on op posite half cycles, eans. for .applyinga'n'out- "of phase voltage to said discharge devices to control. theIperiods of their operation'in' each cycle-and and permitting said second electric discharge ca;

vice to operate. I Y

2. A full wavealternating current control circuit of the character described comprisingapair of'electric discharge devices connected in back to back relation, and means responsiveto the operation of one of said discharge devices for. controlling the operation of the other of said discharge devices, said meansincludin'g a diode and: a parali lel resistance-capacitance network for; normally building up a negativejchar'ge to'be'applied to the other of said discharge devices, said diodeand said network being bridged across theoutput circult of the first of said discharge devices; whereby operation of said first -discharge device reduces the charge built upby said network and controls the operation of said second electric discharge device. 3. A full wave. alternatingcurrent control circult of the character described comprising an electric discharge device, a second electric discharge device coupled to said first electric discharge device, a gas diode and a parallel resistance capacitance network bridged across the output of said first electric discharge device and coupled to the input of said second discharge device for normally applying a negative bias to said second discharge device and means for applying a sginal to said first discharge device to render it operative and limit the charge of said network thru said diode whereby to control the operation 01? said second electric discharge device.

4. A full wave alternating current control circuit of the character described comprising. an electric discharge device, a second electric discharge device connected to said first electric discharge device in back to back relation, means for applying an out of phase biasing voltage to said discharge devices to render them operative over portions of the cycle, a gas diode and a parallel resistance capitance network connected in series and bridged across the output of said first discharge device and to the input of said second discharge device for normally applying a negative bias to said second electric discharge device, and means for applying a biasing signal to said first discharge device to render it operative for controlling the charging up of said network through said gas filled tube, whereby to control the operation of said second discharge device.

ONIE B. RUDOLPH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

